There has been hitherto known an fiber scanning observation apparatus which scans light from an emitting end of an optical fiber toward an object and detects light reflected or scattered by the object or fluorescence or the like generated in the object. In such apparatus, in order to scan the irradiated light on the object, the optical fiber is cantilevered at the tip part thereof, with the emitting end for emitting light being in an oscillatable state, and a drive mechanism such as a piezoelectric element is disposed so as to exert a force in the vicinity of the supporting part, to thereby vibrate the optical fiber.
Helical scan (spiral scan) and Raster scan have been known as exemplary methods of scanning an optical fiber. The spiral scan scans an optical fiber such that the spot of the irradiated light draws spirals. The raster scan vibrates an optical fiber at high speed in one direction while driving the fiber at low speed in other direction perpendicular thereto. In the spiral scan, the vibration frequency is generally set equal to or near the resonance frequency. In the raster scan, the optical fiber may preferably be vibrated near the resonance frequency in the direction of high-speed vibration. For these reasons, the fiber has been conventionally vibratory driven based on the resonance frequency determined based on the design value of the optical fiber scanning apparatus.
Further, in an optical fiber scanning apparatus, sensors for detecting the position of the fiber may be used to obtain beforehand the coordinate data on the irradiation position of light from the optical fiber, as a function of time elapsed from the start of the scan, and in the actual scan of the object, pixel signals detected according to the time elapsed from the start of the scan are mapped on a two-dimensional coordinate, to thereby generate an image.
Cited Document 1 describes an invention which uses scanning position detectors such as a position sensor device (PSD) to obtain a coordinate value of the actual scanning pattern and creates a look-up table having information on the coordinate value, based on which a coordinate to be assigned to each pixel is corrected.